Memory - Studies

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Coding - Study

Baddely (1966) - Coding in STM and LTM 


4 groups of pps, each groupd different list of words

- Acoustically  similar or dissimilar words (group 1&2)

- Semantically similar or dissimilar words (group 3&4)

-once shown the words pps were asked to recall them in the correct order. 

Results & Conclusions

-When asked to recall the words immediatly, pps did worse with acoustically similar words.

-When asked to recall the words after a 20 minuite interval, pps did worse with semantically similar words

-Suggests that STM codes acoustically and LTM codes semantically.

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Capacity - Study

Jacobs (1887) - Capacity of STM


-Jacobs developed a technique to measure digit span 

-Researcher reads out four digits and increases until the pps cannot recall the order correctly

Findings & conclusions

- On average, pps could repeat back 9.3 numbers and 7.3 letters in the correct order immediately after they were presented 

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Capacity - Study

Miller (1956) - Capacity of STM 

-Miller made observations of everyday practice. For example, he noted that things came in sevens: notes on the musical scale, days of the week, deadly sins ect ect

- Miller suggested that the span (or capacity) of STM is about 7 items (+/- 2).

-However Miller also noted that people can recall 5 words as well as they can recall 5 letters. They do this by chunking - grouping sets of digits or letters into units or chunks.

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Duration - Study

Peterson and Peterson (1959) - Duration of STM 


-24 undergraduate students,Each student took part in 8 trails

- Given a trigram to remeber and a 3 digit number to count backwards for 3, 6, 9, 12, 15 or 18 seconds. 

-counting bacwards prevented any mental rehearsal of the trigram

Results & conclusions

- Students recalled (on average) about 80% if the syllables correctly withing a 3 second interval.

-Average recall after 18 seconds fell to about 3% 

-Suggests that the duration of STM without rehearsal is about 18-30 seconds.

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Duration- Study

Bahrick et al (1975) - Duration of LTM


- Pps were 392 Americans aged between 17-74

1) Recognition test: 50 photos from pps high school yearbook

2) Free recall test: pps listed names of their graduating class.

Findings & Conclusions

-Pps tested within 15yrs of graduation were about 90% accurate in photo recognition, those tested after 48 years recalled about 70%

-Free recall was worse than recognition, 15yrs - 60%, 48 yrs - 30%

- Shows that LTM can last a very long time

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WMM Baddely & Hitch (1974)


- Central executive allocates slave systems

- Phonological loop consists of a Phonological store (stores the words you hear) and an articulatory process (allows maintanence rehearsal) 

- Visuo-spatial sketchpad stores visual and/or spatial info when required

-Episodic buffer (added in 2002) temporary storage

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Slave Systems

Phonological loop - deals with auditory info and preserves the order in which the info arrives, It is subdivided into Phonological store (stores the words you hear) and the Articulatory process (allows maintanence rehearsal) 

Visuo - spatial sketchpad - Stores visual and/or spatial info when required. Logie (1995) subdivided the VSS into: visual cache (stores visual data) and inner scribe (records arrangement of objects in visual field) 

Episodic Buffer - added in 2002, it is a temporary store for information. Intergrates visual, spatialm and verbal info from other stores. Maintains a sense of time sequencing - recording events (episodes) that are happening. Links to LTM

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WMM Evaluation

Case of KF support seperate STM stores - Shallice and Warrington carried out a case study of patient KF who had brain damage. He had poor STM ability for verbal communication but could process visual info normally. his phonologucal loop was damaged but other areas of memory were intact. This suggests that there are separate cisual and acoustic storesv. BUT case studies of brain-damage patients may be unreliable as it concerns unique cases of patients who have had traumatic experiences.

+ Dual task perfoemance studies support VSS- Baddely et al found pps had more difficulty doing two cisual tasks (tracking a light and describing the letter F) than doing a visual and verbal task at the same time. THe greater difficulty is becasue both visual tasks compete for the same limited resources. WHen doing a erbal and visual task simultaneously, there is no competition. Therefore dual task performance activity provides evidence for the existence of the visuo-spatial sketchpad. The MSM can't explain this. 

- Lack of clarity over the central executive - Cognitive psychologist suggest that CE is unsatisfactory and doesnt really explain anything. THe CE shoul be more clearly specified than just being simply 'attention'. Some psychologists believe it may consist f spereate components. This means that the WMM hasn't been fully explained. 

+ Word length effect suports the phonological loop - Baddeley et al found that people hav emore difficulty remeber a list of long words than short words. This is the words length effect. This is becasue there is limited space for rehearsal in the articulatory process. Word lentgth efect dissapears if a person is given a repetative task tying up the articulatory process, demonstrating the process at work.

+ Supported from brain studies - Braver et als pps did tass involing CE while they were having their brains scanned. Acivity seen in the prefrontal cortex. Activity in this area increased as the task became harder. This makes sense in terms of the WMM: as it demands on the CE increase, it had to work harder to fufill its function. 


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Explanations of forgetting : Interference theory

Interference: When two pieces of information are in conflict. Forgetting occurs in LTM becasue we can't get acces to meories even though they are available. 

Proactive interference - Old interfered with new 

Retroactive interference - New interferes with the old

Interference is worse when memories are similar. 

This may be because : In PI previously stored info makes new info more difficult to store. In RI new info overwrites previous memories which are similar. 

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Explanations of Forgetting : Study (effects of sim

McGeoch and McDonals (1931) Effects of similarity 

-Participants were asked to learn a list of words to 100% accuracy. 

- Then they were given a new list to learn. The new material vaired in the degree to which it was similar to the old: 

  • Group 1: synonyms -words had the same meanings 
  • Group 2: antonyms - words had opposite meanings
  • Group 3: unrelated
  • Group 4: nonsese syllables
  • Group 5: 3-digit numbers 
  • Group 6: no new list ( control group) 

- Performance depended on the nature of the second list. The most similar material produced teh worst recall. WHen PPs were given very different material, the mean number of items recalled increased. 

- This shows that interference is stronger when the memories are similar. 

-In group 1 it is likely that the words with the same meanings as the original list blocked acess of that the new materal became confused with the old material. 

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Explanations of forgetting : Retrieval failure

Lack of cues can cause retrieval failure - when info is initially placed in memory associated cues are stored at the same time. If these cues are not available at the time of recall, you might not be able to access memories that are acutally there. 

Encoding specificity principle (ESP) - Tulving (1983) suggested that cues help retrieval if the same cues are present at encoding and retrieval. The close the retrieval cue to the originla, the better the cue works. 

Some cues have meaning linked to the memory - some cues are linked to the memory that is to be remebered, in a meaningful way. e.g the cue STM may lead you to recall all sorts of info about short term memory.

Some cues have no meaningful link - other cues are also encoded at the time of learning but not in a meanigful way. 

  • Context-dependent forgetting: when memory retrieval is dependent on an external/enviromental cue ( e.g the weather or a place)
  • State-dependent forgetting when memory retrieval is dependent on an internal cue, state of mind. ( e.g feeling upset, being drunk)
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Explanations of Forgetting : Study (context-depend

Godden & Baddely (1975) context dependent forgetting

-Cues were the contextes where learning and recall took place ( on land or underwater) 

- Deep sea divers learned word lists and were later asked to recal them 

  • Group 1: Learn on land - recall on and
  • Group 2: Learn on land - recall underwater
  • Group 3: Learn underwater -recall on land
  • Group 4: Leanr underwater -  recall underwater

-When the enviromental contexts of learning and reall did not match (i.e conditions 2&3 ) accurate recall was 40% lower than when conditions did match.

-When the external cues available at learning were different from the ones at recall, this lead to retrieval failuredie to lack of cues.

- This study demonstrates context-dependent forgtting because information was not not accessible (was forgetten) when context at recall did not match coding at learning

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Explanations of forgetting : Retrieval failure - E

+ Impressive range of evidence supports this explanation of forgetting - e.g Godden and Baddeley's research with deep sea divers. Eysenc (2010) goes so far as to argue that retrieval failure is perhaps the main reason for forgetting in LTM. Supporting evidence increases teh validity of an explanation, expecially when conducted in real-life situations as well as the highly controlled conditions of the lab.

- Context effects are actually not very strong in real life - Baddeley (1966) argued that different contextshave to be very different in order for the effectsto be seen (e.g land vs water). Learning something in one rom and recalling it in another is unlikley to results in much forgetting because the enviroments are not different enough.The real-life applications of retrieval failure due to contextual cues don't actually explain much forgetting.

- Context effects only occurs when memory is tested in certain ways - Godden and Baddeley (1980) replicated their experiment unsing a recognition test instead of recall. There was no context - dependent effect. Performance was the same in all four conditions whether the enviromental contexts of learning and recall matched or not. This limits retrieval failure as an explanation of forgetting bcaue the prescence or absence of cues only affects memory when you test recall rather than recognition. 

-  ESP cannot be tested and leads to circlar reasoning - When a cue produces succesful recall we assume the cue must have been present at the time of learning. If a cue does not result in successful recall, then we assume that the cue was not encoded at the time of learning. But there is no way to independently establish whether or not the cue has really been encoded.

+  Context-related cues have usedful everyday applications - The application is that when we have trouble remebering something, it is probably worth making the efort to revisist the enviroment in which you first experienced it. This is a basica principle of  the Cognitive interview. 

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EWT: misleading information

Leading questions

Response-bias explanation - wording of a question had no enduring effects on an eyewitness's memory of an event, but influences the kind of answer given. 

Substitution explanation - Wording of a question does affect eyewtiness memory; it interferes with its origincal memory, distorting its accuracy. 

Key study : Loftus and palmer (1974) Leading Questions 

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EWT : Study (Leading questions)

Lofus and Palmer (1974) Leading questions 

-45 pps (students) watched film clips of car accidents and then answered questions about the speed the vehicle was travelling at the time of impact.

- Critical Question : 'About how fast were the cars gong when they hit each other?'

-five groups of pps, each given a different verb in the critical question : hit, contacted, bumoed, collided, or smashed

- The verb 'contacted' produced a mean estimated speed of 31.8 mph. The verb 'smashed' the mean was 40.5 mph

-  The leading question (Verb) biased witnesses recall fo the event. The verb 'smashed' suggested a faster speed of the car than 'contacted' 

Results: Verb/Mean estimate (mph)

  • contacted/ 31.8
  • Bumped/ 34.0
  • Hit/ 38.1
  • Collided/ 39.8
  • Smashed/ 40.8
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EWT : Study (Leading questions)

Lofus and Palmer (1974) Leading questions 

-45 pps (students) watched film clips of car accidents and then answered questions about the speed the vehicle was travelling at the time of impact.

- Critical Question : 'About how fast were the cars gong when they hit each other?'

-five groups of pps, each given a different verb in the critical question : hit, contacted, bumoed, collided, or smashed

- The verb 'contacted' produced a mean estimated speed of 31.8 mph. The verb 'smashed' the mean was 40.5 mph

-  The leading question (Verb) biased witnesses recall fo the event. The verb 'smashed' suggested a faster speed of the car than 'contacted' 

Results: Verb/Mean estimate (mph)

  • contacted/ 31.8
  • Bumped/ 34.0
  • Hit/ 38.1
  • Collided/ 39.8
  • Smashed/ 40.8
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EWT: Misleading information

Post-event discussion (PED)

Memory contamination- When co-witnesses discuss a crime, they mix (mis)information wfrom other witnesses with their own memories

Memory Conformity - Witnesses fo along with each other to win social approval or becasue they belive the other witnesses are right. 

Key study: Gabber et al (2003) Post event discussion

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EWT: Study (misleading information)

Gabbert et al (2003) Post-event discussion 

-Paired pps watched a video of the same crime, but filmed so each pps could see elements in the event that the other could not. 

-Both  pps discussed what they had sen on the video before individually completing a test of recall. 

- 71% of the pps mistakenly recalled aspects of th event tht they had not seen in the video but had picked u pfrom the post event discussion. 

- In a control group, where there was no discussion, there were no errors

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EWT: Misleading information - Evaluation

+ Research into misleading information has real life applications - importnt practical uses for police offices and investigators, important becasue the consequences of inaccurate EWT can be very serious. Psychologist invesitgating EWT can make an important difference to the loves of real people e.g by improving how the legal system works. 

- Loftus and Palmer's study used artificial materials - Pps wathced film clips of accidents, a very different experience from witnessing a read accident (it is less stressful). Using artificial tasks tell us little about how leading questions affect EWT in real crimes or accidents.

- There may be individual differences in accuracy of EWT - Anastasi and Rhodes found that older people were less accurate thatn younger people when giving eyewtiness reports. They also found that all age groups were oe accurate when indetifying people of their own age group. 

- Lab studies of EWT suffer from demand characteristics - Research pps usually want to be helpful and attentive. SO when asked a question and don't know the anser they guess (especially for yes/no questions) Pps might be asked 'did you see the green car?' even if there was not a green car in the film. pps may reply 'yes' becasue it seems a more helpful answer. THis challenges the validity of EWT research. Studies intent to measure the accuracy of eyewitnesses memory but the answers the eyewitness give may not acutally reflect their memories. 

- Many EWT studies lack external validity - Foster et al argues that what you remeber as an eyewitness can have important consequences in the real world, but the same is not true in studies. Ral eyewitnesses search their memory with more effots becasue their testimony may lead to a successful conviction. This is not true in research studies. Therefore EWT accuacy may be greater in the real world becasue of the serious implicationsof their role. 

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EWT: Anxiety - Study

Johnson & Scott (1976) Anxiety has a negative effect

-Pps sat in a waiting rom believing they were going to take part in a lab study.

- Each participant heard an argument in the next room. 

  • low anxiety condition: a man then walked out holding a pen with grease on his hands
  • high anxiety condition:  a man then walked out holding a peper knife covered in blood

-pps were later asked to pick the man from a set of 50 photographs

-49% of pps in the low anxiety condition were able to idnetify him. The correspoding figure for high anxity pps was just 33%

-The 'tunnel theory of memory' argues that a witness' attention is on the earpon (weapn focus), becasue it is a source of danger and anxiety. 

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EWT: Anxiety -Study

Yuille and Cutshall (1986) Anxiety had a positive effect on EWT

- In a realolife crime a gun-shop owner shot a thief dead. There were 21 witnesses, 13 agreed to participate in teh study.

-Pps were interviewed 4-5 months after the incident. Accounts were compared to the police interviews at the time of the shooting

-Witnesses rated how stressed they felt at the time of the incident.

- Witnesses were very accurate and there was little change after 5 months. Some details were less accurate, e.g colours of item, and age/weight/height.

-pps who repoted the hightes levels of stress were the most accurate (88% compared to 75% fro the less-stressed group)  

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EWT: Anxiety

Explaining the contraditcory findings

'Inverted U' theory - Yerkes and Dodson (1908) argue that the relationship between performance and arousal/stress is curvilinear rather rather than linear.


Affects memory - Deffenbacher (1983) found that lower levels of anxiety did produce lower levels of accuracy. Recall accuracy increases with anxiety up to an optimal point. A drastic deline in accuracy is seen when an eyewitness experiences more anxiety than the optimal point.

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